2019 Solution 08

Consider the two circuits below.
Circuit _[a,b]___ is likely to have better _[commonly accepted spec abbreviation or phrase or a clear description]___
For example you might answer like: a, f3dB or b, power supply rejection ratio.
Circuit _a _ is likely to have better _CMRR _
The decoupling from vgnd to ground shorts the signal, removing the ability to reject (or cancel) common mode signals.